I/O instructions
Name Description Code Operation operands operand size
in Read from a port in dest, port transfer value from input port to dest

al, const
ax, const
eax,const

al, dx
ax, dx
eax,dx

byte,byte
word,byte
dword,byte
out Write to a port out port, source transfer value to output port from source

const, al
const, ax
const, eax

dx, al
dx, ax
dx, eax

byte,byte
byte,word
byte,dword